Hi Guys
Following my last post, and the useful subsequent information from you all, I checked out the alternator ripple with my scope and this was fine. I then went on to check the output from the Alternator to the ECU and from the ECU to the warning lamp and here lies the problem!! I have the 1 volt specified with ignition on, however when the engine is running and the battery is charging, the input to the alternator from fuse 36 reads 14.2 volts, exactly the same as the battery voltage, however the output to the ECU from the alternator terminal is about 10.3 volts, so the potential difference is 3.9 volts, which is clearly where the dim warning light is coming from. I have checked the cable resistance back to the ECU from the Alternator and this is well within limits. As a final check I checked the output to the warning lamp from the ECU, and this was identical to the input of 10.3 volts from the Alternator into the ECU!!

So my conclusion after a lot of wasted time is that the Exchange Alternator is faulty, and as you guys know they are not the easiest to change on the Rover 75 . . . . Why is it, that even having purchased a reputable manufacturers exchange unit we get this? I suppose part of the problem is the pressure on prices of replacement parts and possible cut corners in the remanufacturing process, however given that we will get no recompense from the suppliers for a faulty unit, the end loser is ourselves in terms of workshop time used for the testing and subsequent rectification work doing the same job twice!!!

I will post again and confirm the fix once complete, meanwhile thanks to you all for the information, and most of all thanks to UKAT for a great medium through which we can share our problems and have a rant.

Roger